PHASE RELATIONSHIPS IN THE URANIUM-CARBON SYSTEM AS DETERMINED BY CHEMICAL, METALLOGRAPHIC, AND X-RAY DIFFRACTION METHODS

Technical Report · Sun Sep 01 04:00:00 EDT 1963

OSTI ID:4659771

Ferris, L M; Bradley, M J; Gray, R J

Phase identification in the uranium-- carbon system was accomplished by using data obtained by analyzing a series of high-purity as-cast and heat-treated specimens. The specimens were characterized by chemical analyses for uranium, total carbon, free carbon, oxygen, nitrogen, and tungsten; by x-ray diffraction; by metallographic examination; and by the gases evolved on hydrolysis. On hydrolysis, uranium monocarbide yielded predominantly methane; uranium metal (in U-UC alloys), hydrogen; uranium dicarbide, about 40 vol% hydrogen, 15 vol% methane, and 45 vol% C/sub 2/- to C/sub 8/-hydrocarbons; and uranium sesquicarbide, about 60 vol% hydrogen, 40 vol% C/sub 2/- to C/sub 8/- hydrocarbons, and virtually no methane. As-cast specimens with compositions between UC/sub 0.4/ and UC/sub 1.0/ (2 to 4.8 wt% C) were mixtures of uranium metal and uranium monocarbide (UC). Heat-treatments of UC specimens at temperatures between 1275 and 2000 deg C produced no effect, showing that uranium monocarbide is stable in this temperature range. In attempts to prepare UC/sub 2.0/, the maximum combined-C/U ntom ratio obtained was 1.85 plus or minus 0.03 (8.5 wt% C). Specimens with higher total-C/U atom ratios were binary mixtures of temperatures between 1260 and 2000 deg C had no effect on their x-ray-diffraction patterns, hydrolysis products, or combined-C/U atom ratios. No uranium sesquicarbide was detected after heating for 60 hr at 1450 deg C or 240 hr at 1260 deg C; the oxygen and nitrogen concentrations of the specimens were less than 0.1 wt% and 0.01 wt %, respectively. Therefore, uranium dicarbide is a carbon deficientcompound of composition UC/sub 1.85 plus or minus 0.03/ which is thermally stable at least to short heat treatments at temperatures between 1260 and 2000 deg C. As-cast specimens and specimens heat treated above 1900 deg C with compositions between UC and UC/sub 1.85/ (4.8 to 8.5 wt% C) were mixtures of the monocarbide and dicarbide. Heat-treating UC --/sub 1.85/specimens between 1275 and 1720 deg C resulted in the formation of twophase structures between 1275 and 1720 deg C resulted in the formation of two-phase structures containing either UC and U/sub 2/C/sub 3/ or UC/sub 1.5/ and U/sub 2/C/sub 3/, with corresponding changes in microstructures, x-ray-diffraction patterns, and hydrolysis products. No external stress was required to form the sesquicarbide. The sesquicarbide decomposed into monocarbide and dicarbide when heated to 1900 deg C. These results obtained by heat treating UC/sub 1.5/compositions are in agreement with those of other workers who found that U/sub 2/C/sub 3/ decomposed at about 1780 deg C. (auth)

• Research Organization: Oak Ridge National Lab., Tenn.
• DOE Contract Number: W-7405-ENG-26
• NSA Number: NSA-17-037170
• OSTI ID: 4659771
• Report Number(s): ORNL-TM-668; CONF-206-1
• Country of Publication: United States
• Language: English

Related Subjects

CARBON
CASTING
CHEMICAL REACTIONS
CHEMISTRY
DECOMPOSITION
DIFFRACTION
GASES
HEAT TREATMENTS
HIGH TEMPERATURE
HYDROCARBONS
HYDROGEN
HYDROLYSIS
IMPURITIES
METALLOGRAPHY
METHANE
NITROGEN
OXYGEN
QUALITATIVE ANALYSIS
QUANTITATIVE ANALYSIS
TUNGSTEN
URANIUM
URANIUM CARBIDES
X RADIATION